GPS uses a network of satellites to determine location through trilateration. Satellites continuously transmit timing signals, while receivers calculate distance based on signal travel time to intersect with other satellite spheres and determine position at their cross-section. At least 4 satellites are needed - 3 for 2D location and 4 for 3D including altitude. Precise timing is crucial, and receivers correct for clock errors between satellites and receivers. GPS provides navigation, mapping and a wide range of applications based on positioning calculations.